U.S. patent application number 14/134819 was filed with the patent office on 2015-06-25 for low bake temperature curable coating compositions and processes for producing coatings at low bake temperatures.
The applicant listed for this patent is AXALTA COATING SYSTEMS IP CO., LLC. Invention is credited to Jose Antonio Garcia, Kurt A. Hankerson, Eric C. Houze, Sheau-Hwa Ma, Gary W. Nickel, Delson Jayme Trindade, Henry A. Tronco, JR., Ayumu Yokoyama.
Application Number | 20150175834 14/134819 |
Document ID | / |
Family ID | 53399325 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150175834 |
Kind Code |
A1 |
Yokoyama; Ayumu ; et
al. |
June 25, 2015 |
LOW BAKE TEMPERATURE CURABLE COATING COMPOSITIONS AND PROCESSES FOR
PRODUCING COATINGS AT LOW BAKE TEMPERATURES
Abstract
The present invention is directed to a solvent borne low bake
curable coating composition having improved sag resistance and
coatings properties and process for using the same. The composition
includes a crosslinkable component having one or more polymers
having two or more crosslinkable groups, a crosslinking component
comprising one or more crosslinking agents having crosslinking
groups; and a low bake temperature control agent that includes a
rheology component and polyurea. When a layer of a pot mix
resulting from mixing of the crosslinkable and crosslinking
components is applied over a substrate, it has high sag resistance
while providing desired coating properties, such as high gloss and
rapid cure even under low bake cure conditions. The solvent borne
coating compositions is well suited for use in automotive refinish
applications as well as industrial applications, such as
construction and transportation equipment.
Inventors: |
Yokoyama; Ayumu;
(Wallingford, PA) ; Tronco, JR.; Henry A.;
(Springfield, PA) ; Houze; Eric C.; (Mullica Hill,
NJ) ; Ma; Sheau-Hwa; (West Chester, PA) ;
Hankerson; Kurt A.; (Newark, DE) ; Garcia; Jose
Antonio; (Cherry Hill, NJ) ; Nickel; Gary W.;
(Sewell, NJ) ; Trindade; Delson Jayme; (Rochester
Hills, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AXALTA COATING SYSTEMS IP CO., LLC |
Wilmington |
DE |
US |
|
|
Family ID: |
53399325 |
Appl. No.: |
14/134819 |
Filed: |
December 19, 2013 |
Current U.S.
Class: |
427/385.5 ;
524/507 |
Current CPC
Class: |
C08F 220/10 20130101;
C08F 220/06 20130101; C09D 133/06 20130101; C08F 220/06 20130101;
C08F 220/10 20130101; C09D 133/06 20130101; C09D 4/00 20130101 |
International
Class: |
C09D 133/12 20060101
C09D133/12; B05D 3/02 20060101 B05D003/02; C09D 133/08 20060101
C09D133/08 |
Claims
1. A low bake temperature curable coating composition comprising: a
crosslinkable component comprising an acid functional acrylic
copolymer polymerized from a monomer mixture comprising about 2
percent to about 12 percent of one or more carboxylic acid group
containing monomers, percentages based on total weight of the acid
functional acrylic copolymer, a crosslinking component; and a low
bake temperature control agent comprising a rheology component
chosen from an amorphous silica, a clay, or a combination thereof,
the rheology component present in an amount of from about 0.1 to
about 10 weight percent, and about 0.1 weight percent to about 10
weight percent of polyurea, said percentages based on total weight
of the crosslinkable and crosslinking components.
2. The coating composition of claim 1 wherein said acid functional
acrylic copolymer has a GPC weight average molecular weight ranging
from about 8,000 to about 100,000 and a polydispersity ranging from
about 1.05 to about 10.0.
3. The coating composition of claim 1 wherein said acid functional
acrylic copolymer has Tg ranging from about -5.degree. C. to about
+100.degree. C.
4. The coating composition of claim 1 wherein said monomer mixture
comprises one or more functional (meth)acrylate monomers and one or
more non-functional (meth)acrylate monomers.
5. The coating composition of claim 4 wherein said monomer mixture
comprises about 5 percent to about 40 percent based on total weight
of the acid functional acrylic copolymer of said functional
(meth)acrylate monomers.
6. The coating composition of claim 5 wherein said functional
(meth)acrylate monomer is provided with one or more crosslinkable
groups selected from the group consisting of a primary hydroxyl,
secondary hydroxyl and a combination thereof.
7. The coating composition of claim 5 wherein said functional
(meth)acrylate monomer is selected form the group consisting of
hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate,
hydroxyisopropyl(meth)acrylate, hydroxybutyl(meth)acrylate, and a
combination thereof.
8. The coating composition of claim 1 wherein said carboxylic acid
group containing monomer comprises one or more carboxylic acids
selected from the group consisting of (meth)acrylic acid, crotonic
acid, oleic acid, cinnamic acid, glutaconic acid, muconic acid,
undecylenic acid, itaconic acid, crotonic acid, fumaric acid,
maleic acid, and a combination thereof.
9. The coating composition of claim 1 wherein said crosslinking
component comprises a polyisocyanate, melamine or a combination
thereof.
10. The coating composition of claim 1 wherein said polyurea is
produced by polymerizing a monomer mixture comprising one or more
amine monomers, one or more isocyanate monomers and one or more
moderating polymers.
11. The coating composition of claim 10 wherein said amine monomer
is selected from the group consists of a primary amine, secondary
amine, ketimine, aldimine, or a combination thereof.
12. The coating composition of claim 10 wherein said isocyanate
monomer is selected from the group consists of an aliphatic
polyisocyanate, cycloaliphatic polyisocyanate, aromatic
polyisocyanate and a combination thereof.
13. The coating composition of claim 10 wherein said monomer
mixture comprises about 0.5 to about 3 weight percent of said amine
monomer and about 0.5 to about 3 weight percent of isocyanate
monomer, wherein said weight percentages being based on the total
weight of cross-linkable component.
14. The coating composition of claim 1 formulated as a two-pack
coating composition, wherein said crosslinkable component and said
crosslinking component are stored in separate containers.
15. The coating composition of claim 1 formulated as an automotive
OEM composition, automotive refinish composition or industrial
coating composition.
16. The coating composition of claim 1, wherein said crosslinkable
component comprises in a range of from about 2 weight percent to
about 25 weight percent of said acid functional acrylic copolymer,
all percentages being based on the total weight of the
crosslinkable component.
17. A process for producing a coating on a substrate comprising:
(a) mixing a cross-linkable component, a crosslinking component and
a low bake temperature control agent of a low bake temperature
curable coating composition to form a pot-mix, said crosslinkable
component comprising an acid functional acrylic copolymer
polymerized from a monomer mixture comprising about 2 weight
percent to about 12 weight percent of carboxylic acid group
containing monomer based on total weight of the acid functional
acrylic copolymer, and wherein said low bake temperature control
agent comprises a rheology component chosen from an amorphous
silica, a clay, or a combination thereof, the rheology component
present in an amount of about 0.1 weight percent to about 10 weight
percent, and about 0.1 weight percent to about 10 weight percent of
polyurea, said percentages based on total weight of the
crosslinkable and crosslinking components; (b) applying a layer of
said pot-mix over said substrate; and (c) curing said layer at low
bake temperature into said coating on said substrate.
17. The process of claim 16 wherein said low bake temperature
ranges from about 60.degree. F. (15.degree. C.) to about
200.degree. F. (93.degree. C.).
18. The process of claim 16 wherein said substrate is an automotive
body, industrial equipment or construction equipment.
Description
TECHNICAL FIELD
[0001] The present invention relates to curable compositions and
more particularly relates to low VOC (volatile organic component)
low bake temperature curable coating compositions suitable for use
in automotive OEM (original equipment manufacturer) and refinish
applications and processes for producing coatings at low bake
temperatures.
BACKGROUND
[0002] A number of clear and pigmented coating compositions are
utilized in various coatings, such as, for example, primer coats,
basecoats and clearcoats used in automotive coatings, which are
generally solvent based.
[0003] Multi-coat systems were developed to satisfy a need for
improved aesthetics of the coated substrate. A multi-coat system
typically includes a primer coat, followed by a basecoat, which is
typically pigmented and then finally a clearcoat that imparts a
glossy appearance of depth that has commonly been called "the wet
look".
[0004] In order to improve the manufacturing efficiency and also to
lower production costs, it is important in a multi-coat system to
speedily dry (thus lowering production cycle time) and/or cure
intermediate layers (such as basecoats sandwiched between the
primer and clear coats) at lower bake temperatures (thus lowering
manufacturing costs) so that subsequent layers can be applied
without adversely affecting the coatings properties, such as gloss
or bleeding of base coat into the subsequently applied clear coat
layer. One way to ensure the foregoing process is to improve, i.e.,
to increase the sag resistance of a coating composition, especially
the one used for of an intermediate basecoat. Sag resistance is the
resistance of a basecoat layer of a coating composition to sag when
applied over a slanted or vertical substrate surface.
[0005] One approach to improve the sag resistance has been
disclosed in a commonly assigned US Application 20060047051 A1. The
solution is to include amorphous silica in the coating composition.
However, a need still exits to provide for a low VOC coating
composition that can be baked under low bake temperature conditions
at reduced cycle time.
SUMMARY
[0006] In an exemplary embodiment, a low bake temperature curable
coating composition includes:
[0007] a crosslinkable component comprising an acid functional
acrylic copolymer polymerized from a monomer mixture comprising 2
percent to 12 percent of one or more carboxylic acid
group-containing monomers, percentages based on total weight of the
acid functional acrylic copolymer,
[0008] a crosslinking component; and
[0009] a low bake temperature control agent comprising a rheology
component chosen from amorphous silica, a clay, and a combination
thereof, the rheology component present in an amount of about 0.1
weight percent to about 10 weight percent, and about 0.1 weight
percent to about 10 weight percent of polyurea, said percentages
based on total weight of the crosslinkable and crosslinking
components.
[0010] In another exemplary embodiment, a process for producing a
coating on a substrate includes:
[0011] (a) mixing a cross-linkable component, a crosslinking
component and a low bake temperature control agent of a low bake
temperature curable coating composition to form a pot-mix, said
crosslinkable component comprising an acid functional acrylic
copolymer polymerized from a monomer mixture comprising 2 weight
percent to 12 weight percent of carboxylic acid group-containing
monomer based on total weight of the acid functional acrylic
copolymer, and wherein said low bake temperature control agent
comprises a rheology component chosen from an amorphous silica, a
clay, and a combination thereof, the rheology component present in
an amount of about 0.1 weight percent to about 10 weight percent,
and about 0.1 weight percent to about 10 weight percent of
polyurea, said percentages based on total weight of the
crosslinkable and crosslinking components;
[0012] (b) applying a layer of said pot-mix over said substrate;
and
[0013] (c) curing said layer at a low bake temperature into said
coating on said substrate.
DETAILED DESCRIPTION
[0014] The features and advantages of the present invention will be
more readily understood, by those of ordinary skill in the art,
from reading the following detailed description. It is to be
appreciated that certain features of the invention, which are, for
clarity, described above and below in the context of separate
embodiments, may also, be provided in combination in a single
embodiment. Conversely, various features of the invention that are,
for brevity, described in the context of a single embodiment, may
also be provided separately or in any sub-combination. In addition,
references in the singular may also include the plural (for
example, "a" and "an" may refer to one, or one or more) unless the
context specifically states otherwise.
[0015] The use of numerical values in the various ranges specified
in this application, unless expressly indicated otherwise, are
stated as approximations as though the minimum and maximum values
within the stated ranges were both proceeded by the word "about."
In this manner, slight variations above and below the stated ranges
can be used to achieve substantially the same results as values
within the ranges. Also, the disclosure of these ranges is intended
as a continuous range including every value between the minimum and
maximum values.
[0016] As used herein:
[0017] "Two-pack coating composition" means a thermoset coating
composition having two components stored in separate containers.
The containers containing the two components are typically sealed
to increase their shelf life. The components are mixed just prior
to use to form a pot mix, which has a limited pot life, typically
ranging from a few minutes (15 minutes to 45 minutes) to a few
hours (4 hours to 8 hours). The pot mix is applied as a layer of a
desired thickness on a substrate surface, such as an auto body.
After application, the layer dries and cures at low bake cure
temperatures to form a coating on the substrate surface having
desired coating properties, such as, high gloss, mar-resistance and
resistance to environmental etching. Low bake cure temperature
suitable for use herein range from about 60.degree. F. (15.degree.
C.) to about 200.degree. F. (93.degree. C.). In one example, the
low bake curing temperature is in a range of from about 60.degree.
F. (15.degree. C.) to about 110.degree. F. (43.degree. C.), and is
referred to as ambient temperatures or ambient conditions. In
another example, the low bake curing temperature is in a range of
from about 60.degree. F. (15.degree. C.) to about 140.degree. F.
(60.degree. C.). In another example, the low bake curing
temperature is in a range of from about 140.degree. F. (60.degree.
C.) to about 160.degree. F. (71.degree. C.). In yet another
example, the low bake curing temperature is in a range of from
about 160.degree. F. (71.degree. C.) to about 200.degree. F.
(93.degree. C.).
[0018] "Low VOC coating composition" means a coating composition
that includes the range of from about 0.1 kilograms (1.0 pounds per
gallon) to about 0.72 kilograms (6.0 pounds per gallon), preferably
about 0.3 kilograms (2.6 pounds per gallon) to about 0.6 kilograms
(5.0 pounds per gallon) and more preferably about 0.34 kilograms
(2.8 pounds per gallon) to about 0.53 kilograms (4.4 pounds per
gallon) of the solvent per liter of the coating composition. All
VOC's determined under the procedure provided in ASTM D3960.
[0019] "High solids composition" means a coating composition having
solid component of above about 30 percent, preferably in the range
of from about 35 to about 90 percent and more preferably in the
range of from about 40 to about 80 percent, all in weight
percentages based on the total weight of the composition.
[0020] "GPC weight average molecular weight" means a weight average
molecular weight measured by utilizing gel permeation
chromatography. Measurements referred to herein were taken using a
high performance liquid chromatograph (HPLC) supplied by
Hewlett-Packard, Palo Alto, Calif. Unless stated otherwise, the
liquid phase used was tetrahydrofuran and the standard was
polymethyl methacrylate or polystyrene.
[0021] "Tg" (glass transition temperature) referred to herein is
measured in .degree. C. determined by DSC (Differential Scanning
calorimetry).
[0022] "Polydispersity" means GPC weight average molecular weight
divided by GPC number average molecular weight. The lower the
polydispersity (closer to 1), the narrower will be the molecular
weight distribution, which is desired.
[0023] "(Meth)acrylate" means acrylate and methacrylate.
[0024] "Polymer solids" means a polymer in its dry state.
[0025] "Crosslinkable component" means a component that includes a
compound, polymer or copolymer having functional groups positioned
in the backbone of the polymer, pendant from the backbone of the
polymer, terminally positioned on the backbone of the polymer, or a
combination thereof.
[0026] "Crosslinking component" is a component that includes a
compound, polymer or copolymer having groups positioned in the
backbone of the polymer, pendant from the backbone of the polymer,
terminally positioned on the backbone of the polymer, or a
combination thereof, wherein these groups are capable of
crosslinking with the functional groups on the crosslinkable
component (during the curing step) to produce a coating in the form
of crosslinked structures.
[0027] In coating applications, especially the automotive refinish
or OEM applications, a key driver is productivity, i.e., the
ability of a layer of a coating composition to dry rapidly to a
strike-in resistant state such that a subsequently coated layer,
such as a layer formed from a clear coating composition does not
adversely affect the underlying layer. Once the top layer is
applied, the multi-coat system should then cure sufficiently
rapidly without adversely affecting uniformity of color and
appearance. The present invention addresses the forgoing issues by
utilizing a unique crosslinking technology and an additive. Thus,
the present coating composition includes a crosslinkable and
crosslinking component.
[0028] The crosslinkable component includes about 2 weight percent
to about 25 weight percent, preferably about 3 weight percent to
about 20 weight percent, more preferably about 5 weight percent to
about 15 weight percent of one or more acid functional acrylic
copolymers, all percentages being based on the total weight of the
crosslinkable component. If the composition contains excess of the
upper limit of the acid functional acrylic copolymer, the resulting
composition tends to have higher than required application
viscosity. If the composition contains less than the lower limit of
the acid functional copolymer, the resultant coating would have
insignificant strike-in properties for a multi-coat system or flake
orientation control in general.
[0029] The crosslinkable component includes an acid functional
acrylic copolymer polymerized from a monomer mixture that includes
about 2 weight percent to about 12 weight percent, preferably about
3 weight percent to about 10 weight percent, more preferably about
4 weight percent to about 6 weight percent of one or more
carboxylic acid group containing monomers, all percentages being
based on the total weight of the acid functional acrylic copolymer.
If the amount of the carboxylic acid group-containing monomer in
the monomer mixture exceeds the upper limit, the coatings resulting
from such a coating composition would have unacceptable water
sensitivity and if the amount is less than the lower limit, the
resultant coating would have insignificant strike-in properties for
a multi-coat system or flake orientation control in general.
[0030] The acid functional acrylic copolymer preferably has a GPC
weight average molecular weight ranging from about 8,000 to about
100,000, preferably from about 10,000 to about 50,000 and more
preferably from about 12,000 to about 30,000. The copolymer
preferably has a polydispersity ranging from about 1.05 to about
10.0, preferably ranging from about 1.2 to about 8 and more
preferably ranging from about 1.5 to about 5. The copolymer
preferably has a Tg of ranging from about -5.degree. C. to about
+100.degree. C., preferably from about 0.degree. C. to about
80.degree. C. and more preferably from about 10.degree. C. to about
60.degree. C.
[0031] The carboxylic acid group-containing monomers suitable for
use in the present invention include (meth)acrylic acid, crotonic
acid, oleic acid, cinnamic acid, glutaconic acid, muconic acid,
undecylenic acid, itaconic acid, crotonic acid, fumaric acid,
maleic acid, or a combination thereof (Meth)acrylic acid preferred.
It is understood that applicants also contemplate providing the
acid functional acrylic copolymer with carboxylic acid groups by
producing a copolymer polymerized from a monomer mixture that
includes anhydrides of the aforementioned carboxylic acids and then
hydrolyzing such copolymers to provide the resulting copolymer with
carboxylic acid groups. Maleic and itaconic anhydrides are
preferred. Applicants further contemplate hydrolyzing such
anhydrides in them monomer mixture before the polymerization of the
monomer mixture into the acid functional acrylic copolymer.
[0032] It is believed, without reliance thereon, that the presence
of carboxylic acid groups in the copolymer of the present invention
appears to increase viscosity of the resulting coating composition
due to physical network formed by the well-known hydrogen bonding
of carboxyl groups. As a result, such increased viscosity, assists
in strike-in properties in multi-coat systems and flake orientation
control in general.
[0033] The monomer mixture suitable for use in the present
invention includes about 5 percent to about 40 percent, preferably
about 10 percent to about 30 percent, all based on total weight of
the acid functional acrylic copolymer of one or more functional
(meth)acrylate monomers. It should be noted that if the amount of
the functional (meth)acrylate monomers in the monomer mixture
exceeds the upper limit, the pot life of the resulting coating
composition is reduced and if less than the lower limit is used, it
adversely affects the resulting coating properties, such as
durability. The functional (meth)acrylate monomer is provided with
one or more crosslinkable groups selected from a primary hydroxyl,
secondary hydroxyl, or a combination thereof.
[0034] Some of suitable hydroxyl containing (meth)acrylate monomers
have the following structure:
##STR00001##
wherein R is H or methyl and X is a divalent moiety, which can be
substituted or unsubstituted C.sub.1 to C.sub.18 linear aliphatic
moiety, or substituted or unsubstituted C.sub.3 to C.sub.18
branched or cyclic aliphatic moiety. Some of the suitable
substituents include nitrile, amide, halide, such as chloride,
bromide, fluoride, acetyl, aceotoacetyl, hydroxyl, benzyl and aryl.
Some specific hydroxyl containing (meth)acrylate monomers in the
monomer mixture include 2-hydroxyethyl(meth)acrylate,
2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, and
4-hydroxybutyl(meth)acrylate.
[0035] The monomer mixture can also include one or more
non-functional (meth)acrylate monomers. As used here,
non-functional groups are those that do not crosslink with a
crosslinking component. Some of suitable non-functional C1 to C20
alkyl(meth)acrylates include methyl(meth)acrylate,
ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate,
pentyl(meth)acrylate, hexyl(meth)acrylate, octyl(meth)acrylate,
nonyl(meth)acrylate, isodecyl(meth)acrylate, and
lauryl(meth)acrylate; branched alkyl monomers, such as
isobutyl(meth)acrylate, t-butyl(meth)acrylate and
2-ethylhexyl(meth)acrylate; and cyclic alkyl monomers, such as
cyclohexyl(meth)acrylate, methylcyclohexyl(meth)acrylate,
trimethylcyclohexyl(meth)acrylate,
tertiarybutylcyclohexyl(meth)acrylate and isobornyl(meth)acrylate.
Isobornyl(meth)acrylate and butyl acrylate are preferred.
[0036] The monomer mixture can also include one or more of other
monomers for the purpose of achieving the desired properties, such
as hardness, appearance and mar resistance. Some of the other such
monomers include, for example, styrene, .alpha.-methyl styrene,
acrylonitrile and methacrylonitrile. When included, preferably, the
monomer mixture includes such monomers in the range of about 5
percent to about 30 percent, all percentages being in weight
percent based on the total weight of the polymers solids. Styrene
is preferred.
[0037] Any conventional bulk or solution polymerization process can
be used to produce the acid functional acrylic copolymer of the
present invention. One of the suitable processes for producing the
copolymer of the present invention includes free radically solution
polymerizing the aforedescribed monomer mixture.
[0038] The polymerization of the monomer mixture can be initiated
by adding conventional thermal initiators, such as azos exemplified
by Vazo.RTM. 64 supplied by DuPont Company, Wilmington, Del.; and
peroxides, such as t-butyl peroxy acetate. The molecular weight of
the resulting copolymer can be controlled by adjusting the reaction
temperature, the choice and the amount of the initiator used, as
practiced by those skilled in the art.
[0039] The crosslinking component of the present invention includes
one or more polyisocyanates, melamines, or a combination thereof.
Polyisocyanates are preferred.
[0040] Typically, the polyisocyanate is provided with in the range
of about 2 to about 10, preferably about 2.5 to about 8, more
preferably about 3 to about 5 isocyanate functionalities.
Generally, the ratio of equivalents of isocyanate functionalities
on the polyisocyanate per equivalent of all of the functional
groups present in the crosslinking component ranges from about
0.5/1 to about 3.0/1, preferably from about 0.7/1 to about 1.8/1,
more preferably from about 0.8/1 to about 1.3/1. Some suitable
polyisocyanates include aromatic, aliphatic, or cycloaliphatic
polyisocyanates, trifunctional polyisocyanates and isocyanate
functional adducts of a polyol and difunctional isocyanates. Some
of the particular polyisocyanates include diisocyanates, such as
1,6-hexamethylene diisocyanate, isophorone diisocyanate,
4,4'-biphenylene diisocyanate, toluene diisocyanate, biscyclohexyl
diisocyanate, tetramethylene xylene diisocyanate, ethyl ethylene
diisocyanate, 1-methyltrimethylene diisocyanate, 1,3-phenylene
diisocyanate, 1,5-napthalene diisocyanate,
bis-(4-isocyanatocyclohexyl)-methane and 4,4'-diisocyanatodiphenyl
ether.
[0041] Some of the suitable trifunctional polyisocyanates include
triphenylmethane triisocyanate, 1,3,5-benzene triisocyanate, and
2,4,6-toluene triisocyanate. Trimers of diisocyanate, such as the
trimer of hexamethylene diisocyanate sold under the trademark
Desmodur.RTM.N-3390 by Bayer Corporation of Pittsburgh, Pa. and the
trimer of isophorone diisocyanate are also suitable. Furthermore,
trifunctional adducts of triols and diisocyanates are also
suitable. Trimers of diisocyanates are preferred and trimers of
isophorone and hexamethylene diisocyanates are more preferred.
[0042] Typically, the coating composition can include about 0.1
weight percent to about 40 weight percent, preferably, about 15
weight percent to about 35 weight percent, and more preferably
about 20 weight percent to about 30 weight percent of the melamine,
wherein the percentages are based on total weight of composition
solids.
[0043] Some of the suitable melamines include monomeric melamine,
polymeric melamine-formaldehyde resin or a combination thereof. The
monomeric melamines include low molecular weight melamines which
contain, on an average, three or more methylol groups etherized
with a C1 to C5 monohydric alcohol such as methanol, n-butanol, or
isobutanol per triazine nucleus, and have an average degree of
condensation up to about 2 and preferably in the range of about 1.1
to about 1.8, and have a proportion of mononuclear species not less
than about 50 percent by weight. By contrast the polymeric
melamines have an average degree of condensation of more than about
1.9. Some such suitable monomeric melamines include alkylated
melamines, such as methylated, butylated, isobutylated melamines
and mixtures thereof. Many of these suitable monomeric melamines
are supplied commercially. For example, Cytec Industries Inc., West
Patterson, N.J. supplies Cymel.RTM. 301 (degree of polymerization
of 1.5, 95% methyl and 5% methylol), Cymel.RTM. 350 (degree of
polymerization of 1.6, 84% methyl and 16% methylol), 303, 325, 327,
370 and XW3106, which are all monomeric melamines Suitable
polymeric melamines include high amino (partially alkylated, --N,
--H) melamine known as Resimene.RTM. BMP5503 (molecular weight 690,
polydispersity of 1.98, 56% butyl, 44% amino), which is supplied by
Solutia Inc., St. Louis, Mo., or Cymel.RTM.1158 provided by Cytec
Industries Inc., West Patterson, N.J. Cytec Industries Inc. also
supplies Cymel.RTM. 1130 @ 80 percent solids (degree of
polymerization of 2.5), Cymel.RTM. 1133 (48% methyl, 4% methylol
and 48% butyl), both of which are polymeric melamines
[0044] If desired, including appropriate catalysts in the
crosslinkable component can accelerate the curing process of a
potmix of the coating composition.
[0045] When the crosslinking component includes polyisocyanate, the
crosslinkable component of the coating composition preferably
includes a catalytically active amount of one or more catalysts for
accelerating the curing process. Generally, a catalytically active
amount of the catalyst in the coating composition ranges from about
0.001 percent to about 5 percent, preferably ranges from about
0.005 percent to about 2 percent, more preferably ranges from about
0.01 percent to about 1 percent, all in weight percent based on the
total weight of crosslinkable and crosslinking component solids. A
wide variety of catalysts can be used, such as, tin compounds,
including dibutyl tin dilaurate and dibutyl tin diacetate; tertiary
amines, such as, triethylenediamine. These catalysts can be used
alone or in conjunction with carboxylic acids, such as, acetic
acid. One of the commercially available catalysts, sold under the
trademark, Fastcat.RTM. 4202 dibutyl tin dilaurate by Arkema North
America, Inc. Philadelphia, Pa., is particularly suitable.
[0046] When the crosslinking component includes melamine, it also
preferably includes a catalytically active amount of one or more
acid catalysts to further enhance the crosslinking of the
components on curing. Generally, the catalytically active amount of
the acid catalyst in the coating composition ranges from about 0.1
percent to about 5 percent, preferably ranges from about 0.1
percent to about 2 percent, more preferably ranges from about 0.5
percent to about 1.2 percent, all in weight percent based on the
total weight of crosslinkable and crosslinking component solids.
Some suitable acid catalysts include aromatic sulfonic acids, such
as dodecylbenzene sulfonic acid, para-toluenesulfonic acid and
dinonylnaphthalene sulfonic acid, all of which are either unblocked
or blocked with an amine, such as dimethyl oxazolidine and
2-amino-2-methyl-1-propanol, n,n-dimethylethanolamine or a
combination thereof. Other acid catalysts that can be used are
strong acids, such as phosphoric acids, more particularly phenyl
acid phosphate, which may be unblocked or blocked with an
amine.
[0047] The crosslinkable component of the coating composition can
further include in the range of from about 0.1 percent to about 95
percent, preferably in the range of from about 10 percent to about
90 percent, more preferably in the range of from about 20 percent
to about 80 percent and most preferably in the range of about 30
percent to about 70 percent, all based on the total weight of the
crosslinkable component of an acrylic polymer, a polyester or a
combination thereof. Applicants have discovered that by adding one
or more the foregoing polymers to the crosslinkable component, the
coating composition resulting therefrom provides coating with
improved sag resistance, and flow and leveling properties.
[0048] The acrylic polymer suitable for use in the present
invention can have a GPC weight average molecular weight exceeding
2000, preferably in the range of from about 3000 to about 20,000,
and more preferably in the range of about 4000 to about 10,000. The
Tg of the acrylic polymer varies in the range of from 0.degree. C.
to about 100.degree. C., preferably in the range of from about
10.degree. C. to about 80.degree. C.
[0049] The acrylic polymer suitable for use in the present
invention can be conventionally polymerized from typical monomers,
such as alkyl(meth)acrylates having alkyl carbon atoms in the range
of from 1 to 18, preferably in the range of from 1 to 12 and
styrene and functional monomers, such as, hydroxyethyl acrylate and
hydroxyethyl methacrylate.
[0050] The polyester suitable for use in the present invention can
have a GPC weight average molecular weight exceeding 1500,
preferably in the range of from about 1500 to about 100,000, more
preferably in the range of about 2000 to about 50,000, still more
preferably in the range of about 2000 to about 8000 and most
preferably in the range of from about 2000 to about 5000. The Tg of
the polyester varies in the range of from about -50.degree. C. to
about +100.degree. C., preferably in the range of from about
-20.degree. C. to about +50.degree. C.
[0051] The polyester suitable for use in the present invention can
be conventionally polymerized from suitable polyacids, including
cycloaliphatic polycarboxylic acids, and suitable polyols, which
include polyhydric alcohols. Examples of suitable cycloaliphatic
polycarboxylic acids are tetrahydrophthalic acid, hexahydrophthalic
acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic
acid, 1,4-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic
acid, endomethylenetetrahydrophthalic acid,
tricyclodecanedicarboxylic acid, endoethylenehexahydrophthalic
acid, camphoric acid, cyclohexanetetracarboxylic and
cyclobutanetetracarboxylic acid. The cycloaliphatic polycarboxylic
acids can be used not only in their cis but also in their trans
form and as a mixture of both forms. Examples of suitable
polycarboxylic acids, which, if desired, can be used together with
the cycloaliphatic polycarboxylic acids, are aromatic and aliphatic
polycarboxylic acids, such as, for example, phthalic acid,
isophthalic acid, terephthalic acid, halogenophthalic acids, such
as, tetrachloro- or tetrabromophthalic acid, adipic acid, glutaric
acid, azelaic acid, sebacic acid, fumaric acid, maleic acid,
trimellitic acid, and pyromellitic acid.
[0052] Suitable polyhydric alcohols include ethylene glycol,
propanediols, butanediols, hexanediols, neopentylglycol, diethylene
glycol, cyclohexanediol, cyclohexanedimethanol,
trimethylpentanediol, ethylbutylpropanediol, ditrimethylolpropane,
trimethylolethane, trimethylolpropane, glycerol, pentaerythritol,
dipentaerythritol, tris(hydroxyethyl)isocyanate, polyethylene
glycol and polypropylene glycol. If desired, monohydric alcohols,
such as, for example, butanol, octanol, lauryl alcohol, ethoxylated
or propoxylated phenols may also be included along with polyhydric
alcohols. The details of polyester suitable for use in the present
invention are further provided in the U.S. Pat. No. 5,326,820,
which is hereby incorporated herein by reference. One commercially
available polyester, which is particularly preferred, is
SCD.RTM.-1040 polyester, which is supplied by Etna Product Inc.,
Chagrin Falls, Ohio.
[0053] The crosslinkable component can further include one or more
reactive oligomers, such as those reactive oligomers disclosed in
U.S. Pat. No. 6,221,494, which are incorporated herein by
reference; and non-alicyclic (linear or aromatic) oligomers, if
desired. Such non-alicyclic-oligomers can be made by using
non-alicyclic anhydrides, such as succinic or phthalic anhydrides,
or mixtures thereof. Caprolactone oligomers described in U.S. Pat.
No. 5,286,782 incorporated herein by reference can also be
used.
[0054] The crosslinkable component of the coating composition can
further include one or more modifying resins, which are also known
as non-aqueous dispersions (NADs). Such resins are sometimes used
to adjust the viscosity of the resulting coating composition. The
amount of modifying resin that can be used typically ranges from
about 10 percent to about 50 percent, all percentages being based
on the total weight of crosslinkable component solids. The weight
average molecular weight of the modifying resin generally ranges
from about 20,000 to about 100,000, preferably ranges from about
25,000 to about 80,000 and more preferably ranges from about 30,000
to about 50,000.
[0055] The crosslinkable or crosslinking component of coating
composition of the present invention, typically contains at least
one organic solvent which is typically selected from the group
consisting of aromatic hydrocarbons, such as, petroleum naphtha or
xylenes; ketones, such as, methyl amyl ketone, methyl isobutyl
ketone, methyl ethyl ketone or acetone; esters, such as, butyl
acetate or hexyl acetate; and glycol ether esters, such as
propylene glycol monomethyl ether acetate. The amount of organic
solvent added depends upon the desired solids level as well as the
desired amount of VOC of the composition. If desired, the organic
solvent may be added to both components of the binder. High solids
and low VOC coating composition is preferred.
[0056] Applicants have made a surprise discovery that when the
following low bake temperature control agent is included with
either the crosslinkable component, the crosslinking component, or
both of the coating composition (preferably with the crosslinkable
component), the sag resistance of the layer applied over a
substrate surface can be improved under the low bake temperature
condition, which is the desired outcome of the present invention.
The low bake temperature control agent of the present invention
includes a rheology component. In an exemplary embodiment, the
rheology component includes an amorphous silica, a clay, or a
combination of both. In another exemplary embodiment, the low bake
temperature control agent includes about 0.1 weight percent to
about 10 weight percent, preferably about 0.3 weight percent to
about 5 weight percent, more preferably about 0.5 weight percent to
about 2 weight percent of the rheology component, and in the range
of about 0.1 weight percent to about 10 weight percent, preferably
in the range of about 0.3 weight percent to about 5 weight percent
and more preferably in the range of about 0.5 weight percent to
about 2 weight percent of polyurea, the weight percentages being
based on total weight of the crosslinkable and crosslinking
components of the low bake curable coating composition of the
present invention. If too little silica and polyurea are used (less
than the aforecited ranges) no advantage can be seen and if too
much silica and polyurea are used (more than the aforecited
ranges), the resulting coating surface becomes rough.
[0057] The amorphous silica suitable for use in the present
invention includes colloidal silica, which has been partially, or
totally surface modified through the silanization of hydroxyl
groups on the silica particle, thereby rendering part or all of the
silica particle surface hydrophobic. Examples of suitable
hydrophobic silica include AEROSIL R972, AEROSIL R812, AEROSIL
OK412, AEROSIL TS-100 and AEROSIL R805, all commercially available
from Evonik Industries AG, Essen, Germany Particularly preferred
fumed silica is available from Evonik Industries AG, Essen, Germany
as AEROSIL R 812. Other commercially available silica include
SIBELITE.RTM. M3000 (Cristobalite), SIL-CO-SIL.RTM., ground silica,
MIN-U-SIL.RTM., micronized silica, all supplied by U.S. Silica
Company, Berkeley Springs, West Va.
[0058] The silica can be dispersed in the copolymer by a milling
process using conventional equipment such as high-speed blade
mixers, ball mills, or sand mills. Preferably, the silica is
dispersed separately in the acrylic polymer described earlier and
then the dispersion can be added to the crosslinkable component of
the coating composition.
[0059] The clay suitable for use herein can include clay, dispersed
clay, or a combination thereof. Examples of commercially available
clay products include bentonite clay available as BENTONE.RTM. from
Elementis Specialties, London, United Kingdom, and GARAMITE.RTM.
clay available from Southern Clay Products, Gonzales, Tex., USA,
under respective registered trademarks. BENTONE.RTM. 34 dispersion
described in U.S. Pat. No. 8,357,456 and GARAMITE.RTM. dispersion
described in U.S. Pat. No. 8,227,544, and a combination of the two
are suitable. A combination of the silica and the clay such as the
aforementioned BENTONE.RTM., the GARAMITE.RTM., or dispersions
thereof, also can be used.
[0060] The polyurea suitable for use in the low bake temperature
control agent is obtained from polymerization of a monomer mixture
that includes about 0.5 to about 3 weight percent of the amine
monomers, about 0.5 to about 3 weight percent of the isocyanate
monomers, and about 94 to about 99 weight percent of a moderating
polymer. The amine monomer is selected from the group consists of a
primary amine, secondary amine, ketimine, aldimine, or a
combination thereof. Benzyl amine is preferred. The isocyanate
monomer is selected from the group consisting of an aliphatic
polyisocyanate, cycloaliphatic polyisocyanate, aromatic
polyisocyanate and a combination thereof. The preferred isocyanate
monomer is 1, 6 hexamethylene diisocyanate. The moderating polymer
can be one or more of the aforedescribed polymers. The acrylic
polymers or polyesters are preferred.
[0061] Preferably, the polyurea is produced by mixing one or more
of the moderating polymers with the amine monomers and then
isocyanate monomers are added over time under ambient
conditions.
[0062] The sag resistance of a layer from a pot mix resulting from
mixing of the crosslinkable and crosslinking components of the
current coating composition when applied over a substrate is in the
range of from about 5 (127 Micrometers) to about 20 mils (508
micrometers), as measured under ASTM test D4400-99. The higher the
number, the higher will be the desired sag resistance.
[0063] The coating composition is preferably formulated as a
two-pack coating composition wherein the crosslinkable component is
stored in a separate container from the crosslinking component,
which is mixed to form a pot mix just before use.
[0064] The coating composition is preferably formulated as an
automotive OEM composition or as an automotive refinish
composition. These compositions can be applied as a basecoat or as
a pigmented monocoat topcoat over a substrate. These compositions
require the presence of pigments. Typically, a pigment-to-binder
ratio of about 1.0/100 to about 200/100 is used depending on the
color and type of pigment used. The pigments are formulated into
mill bases by conventional procedures, such as, grinding, sand
milling, and high speed mixing. Generally, the mill base comprises
pigment and a dispersant in an organic solvent. The mill base is
added in an appropriate amount to the coating composition with
mixing to form a pigmented coating composition.
[0065] Any of the conventionally used organic and inorganic
pigments, such as white pigments, for example, titanium dioxide,
color pigments, metallic flakes, for example, aluminum flakes,
special effects pigments, for example, coated mica flakes and
coated aluminum flakes, and extender pigments can be used.
[0066] The coating composition can also include other conventional
formulation additives, such as wetting agents, leveling and flow
control agents, for example, Resiflow.RTM. S (polybutylacrylate),
BYK.RTM. 320 and 325 (high molecular weight polyacrylates),
BYK.RTM. 347 (polyether-modified siloxane), defoamers, surfactants
and emulsifiers to help stabilize the composition. Other additives
that tend to improve mar resistance can be added, such as,
silsesquioxanes and other silicate-based micro-particles.
[0067] To improve weatherability of the clear finish of the coating
composition, about 0.1% to about 5% by weight, based on the weight
of the composition solids, of an ultraviolet light stabilizer or a
combination of ultraviolet light stabilizers and absorbers can be
added. These stabilizers include ultraviolet light absorbers,
screeners, quenchers and specific hindered amine light stabilizers.
Also, about 0.1% to about 5% by weight, based on the weight of the
composition solids, of an antioxidant can be also added. Most of
the foregoing stabilizers are supplied by BASF, Florham Park,
N.J.
[0068] The coating composition of the present invention is
preferably formulated in the form of a two-pack coating
composition. The present invention is particularly useful as a
basecoat for outdoor articles, such as automobile and other vehicle
body parts. A typical auto or truck body is produced from a steel
sheet or a plastic or a composite substrate. For example, the
fenders may be of plastic or a composite and the main portion of
the body of steel. If steel is used, it is first treated with an
inorganic rust-proofing compound, such as, zinc or iron phosphate,
called an E-coat and then a primer coating is applied generally by
electrodeposition. Typically, these electrodeposition primers are
epoxy-modified resins crosslinked with a polyisocyanate and are
applied by a cathodic electrodeposition process. Optionally, a
primer can be applied over the electrodeposited primer, usually by
spraying, to provide better appearance and/or improved adhesion of
a base coating or a mono coating to the primer.
[0069] The present invention is also directed to a process for
producing a multi-coat system on a substrate. The process includes
the following process steps:
[0070] The cross-linkable component of the aforedescribed coating
composition of the present invention is mixed with the crosslinking
component of the coating composition to form a pot-mix. Generally,
the crosslinkable component and the crosslinking component are
mixed just prior to application to form a pot mix. The mixing can
take place though a conventional mixing nozzle or separately in a
container.
[0071] A layer of the pot mix generally having a thickness in the
range of about 15 micrometers to about 200 micrometers is applied
over a substrate, such as an automotive body or an automotive body
that has precoated with a conventional E-coat followed by a
conventional primer, or a conventional primer. The foregoing
application step can be conventionally accomplished by spraying,
electrostatic spraying, commercially supplied robot spraying
system, roller coating, dipping, flow coating or brushing the pot
mix over the substrate. The layer after application is flashed,
i.e., exposed to air, to reduce the solvent content from the potmix
layer to produce a strike-in resistant layer. The time period of
the flashing step ranges from about 5 to about 15 minutes. Then a
layer of a conventional clearcoat composition having a thickness in
the range of about 15 micrometers to about 200 micrometers is
conventionally applied by the application means described earlier
over the strike-in resistant layer to form a multi-layer system on
the substrate. Any suitable conventional clear coating compositions
can be used in the multi-coat system of the present invention. For
example, suitable clearcoats for use over the basecoat of this
invention include solvent borne organosilane polymer containing
clear coating composition disclosed U.S. Pat. No. 5,244,696;
solvent borne polyisocyanate crosslinked clear coating composition,
disclosed in U.S. Pat. No. 6,433,085; clear thermosetting
compositions containing epoxy-functional polymers disclosed in U.S.
Pat. No. 6,485,788; wherein all of the forgoing patents are hereby
incorporated herein by reference.
[0072] The multi-layer system is then cured into said multi-coat
system under low bake temperatures. Under typical automotive OEM
applications, the multi-layer system can be typically cured at low
bake temperatures in about 10 to about 60 minutes. It is further
understood that the actual curing time can depend upon the
thickness of the applied layer, the cure temperature, humidity and
on any additional mechanical aids, such as fans, that assist in
continuously flowing air over the coated substrate to accelerate
the cure rate. It is understood that actual curing temperature
would vary depending upon the catalyst and the amount thereof,
thickness of the layer being cured and the amount of the
crosslinking component utilized. For example, the curing step can
be accelerating by adding a catalytically active amount of a
catalyst or acid catalyst to the composition.
[0073] It should be noted that if desired the present invention
also includes a method of applying a layer of the aforedescribed
pot mix, which is then cured to produce a coating, such as a
basecoat, on a substrate that may or may not include other
previously applied coatings, such as an E-coat or a primer
coat.
[0074] The suitable substrates for applying the coating composition
of the present invention include automobile bodies, any and all
items manufactured and painted by automobile sub-suppliers, frame
rails, commercial trucks and heavy duty truck bodies, including but
not limited to beverage bodies, utility bodies, ready mix concrete
delivery vehicle bodies, waste hauling vehicle bodies, and fire and
emergency vehicle bodies, as well as any potential attachments or
components to such truck bodies, buses, farm and construction
equipment, truck caps and covers, commercial trailers, consumer
trailers, recreational vehicles, including but not limited to,
motor homes, campers, conversion vans, vans, pleasure vehicles,
pleasure craft snow mobiles, all terrain vehicles, personal
watercraft, motorcycles, boats, and aircraft. The substrate further
includes industrial and commercial new construction and maintenance
thereof; cement and wood floors; leather; walls of commercial and
residential structures, such office buildings and homes; amusement
park equipment; concrete surfaces, such as parking lots and drive
ways; asphalt and concrete road surface, wood substrates, marine
surfaces; outdoor structures, such as bridges, towers; coil
coating; railroad cars; printed circuit boards; machinery; OEM
tools; signage; fiberglass structures; sporting goods; and sporting
equipment.
EXAMPLES
Test Procedures
[0075] Sag Resistance
[0076] Sag resistance was measured by using ASTM test D4400-99.
[0077] Distinctness of Image (DOI)
[0078] DOI was measured using a Hunterlab Model RS 232 (HunterLab,
Reston, Va.).
[0079] Surface Roughness
[0080] Orange Peel.RTM. of base coat dry film was measured by using
ASTM D3451.
Procedure 1
Preparation of Acrylic Polymers
[0081] Acrylic polymers were formed by similar free-radical
copolymerization as described above with different monomer ratios
as described below. A reactor equipped with a stirrer, reflux
condenser and under nitrogen, was charged with 13.7 parts
t-butylacetate and heated to reflux at approximately 96.degree. C.
A monomer mixture of 14.6 parts by weight of methyl methacrylate,
5.9 parts by weight of styrene, 11.7 parts by weight of
hydroxyethyl methacrylate, 14.6 parts by weight of n-butyl
acrylate, 11.7 parts by weight of 2-ethylhexyl methacrylate, and
1.2 parts by weight of t-butylacetate was premixed. An initiator
mixture of 3.4 parts Vazo.RTM.67 thermal initiator (Vazo.RTM.67 is
available from E.I. DuPont de Nemours and Company, Wilmington,
Del., USA) and 23.2 parts t-butylacetate was premixed. The monomer
mixture was fed over 360 minutes at reflux simultaneously with the
initiator mixture. The initiator mixture was further fed over 390
minutes. After the initiator mixture feed was complete, the
reaction mixture was held for 60 minutes at reflux and then cooled
to room temperature.
[0082] The resulting acrylic polymer produced herein had the
following characteristics: a calculated Tg of +17.6.degree. C.,
solids 60%, Gardner-Holdt viscosity Y+1/4, and weight average
molecular weight (Mw) of 10,000.
Procedure 2
Preparation of Polyurea
[0083] In a reactor, 1.7 parts by weight percent of benzyl amine
(available from BASF, Florham Park, N.J.) was added to 1.34 parts
by weight percent of 1,6 Hexamethylene Diiscocyanate, in the
presence of 96.36 parts by weight percent of the acrylic polymer
(Tg=17.6.degree. C.) from Procedure 1. The mixture was stirred for
5 minutes to produce the polyurea.
Procedure 3
Preparation of Low Bake Temperature Control Agent
[0084] In a conventional milling device, 9 parts by weight percent
of Aerosil.RTM. R 805 fumed silica powder supplied by Evonik
Industries AG, Essen, Germany was milled with 30 parts by weight
percent of the acrylic polymer from Procedure 1 and 61 parts by
weight percent of butyl acetate to a fineness of 7.5 to 8.0 as
measured on a Hegman gauge. Then, 50 parts by weight percent of
this silica dispersion was let down with 50 parts by weight percent
of the polyurea from Procedure 2 to produce the low bake
temperature control agent of the present invention. The
BENOTONE.RTM. dispersion, GARAMITE.RTM. dispersion, or a
combination thereof can also be let down at 50 parts by weight
percent with 50 parts by weight of the polyuria. A combination of
the silica dispersion, BENTONE.RTM. dispersion, and GARAMITE.RTM.
dispersion can also be used.
[0085] Tables below show the formulations of the comparative
examples and an example of the present invention:
TABLE-US-00001 TABLE 1 Coating System of Comparative Example 1
[Base coat having a dry cured coating thickness of 1.5 mils (38.1
microns) coated with Imron .RTM. Elite clear coat having a dry
cured coating thickness of 2 mils (50.8 microns) both bake cured
simultaneously for 30 minutes at high bake temperature of
180.degree. F. (82.2.degree. C.)] Base Coat Ingredients In grams
Polyurea binder prepared by Procedure 2 0 Low bake temperature
control agent 0 prepared by Procedure 3 Silica dispersion.sup.(1) 0
Acid functional acrylic copolymer.sup.(2) 250 Polyester.sup.(3) 197
Imron .RTM. Yellow tint PT 144 3 Imron .RTM. Magenta tint PT 164 6
Imron .RTM. Black tint PT 105 19 Imron .RTM. Transparent yellow
oxide tint PT 101 183 Imron .RTM. Medium fine aluminum tint PT 159
110 Ethyl acetate from Eastman Chemical, 65 Kingsport, Tennessee
Imron .RTM. Activator 15305S (in crosslinking 250 component Total
1051 Test Results Basecoat Sag dry film thickness 2 mils (50.8
microns) R (orange peel) at BC dry film thickness 5 of 1.5 mils
(38.1 microns) measured by ASTM D3451 DOI at Base Coat dry film
thickness of 65 1.5 mils (38.1 microns) measured by ASTM D5767 Test
Observations weak sag resistance Unless stated otherwise, all the
ingredients were supplied by Axalta Coating Systems, LLC of
Wilmington, Delaware. Note: .sup.(1)The silica dispersion was
prepared according to US Patent Publication 2006/0047051, Table 6,
[0080]-[0081], herein incorporated by reference. .sup.(2)The acid
functional acrylic copolymer was prepared according to Acid
Functional Acrylic Copolymer 2: styrene/butyl acrylate/2-ethylhexyl
acrylate/isobornyl acrylate/hydroxypropyl
methacrylate/2-hydroxyethyl mathacrylate/methacrylaic acid:
15.0/30.0/20.0/15.0/7.5/7.5/5.0% by weight. The resulting polymer
solution was clear and had a solid content of about 65.5% and a
Gardner-Holt viscosity of W-1/2. The polymer had a GPC Mw of 15,049
and GPC Mn of 4,789 based on GPC using polystyrene as the standard
and a Tg of +3.7.degree. C. as measured by DSC, as described in US
Patent Publication No. 2006/0047051 A1, herein incorporated by
reference. .sup.(3)Polyester was prepared according to US Patent
Publication 2006/0047051, Table 5, [0078]-[0079], herein
incorporated by reference.
TABLE-US-00002 TABLE 2 Coating System of Comparative Example 2
[Base coat having a dry cured coating thickness of 1.5 mils (38.1
microns) coated with Imron .RTM. Elite clear coat having a dry
cured coating thickness of 2 mils (50.8 microns) both bake cured
simultaneously for 30 minutes at high bake temperature of
180.degree. F. (82.2.degree. C.)] Base Coat Ingredients In grams
Polyurea binder prepared by Procedure 2 0 Low bake temperature
control agent 0 prepared by Procedure 3 Silica dispersion (1) 224
Acid functional acrylic copolymer (2) 76 Polyester (3) 146 Imron
.RTM. Yellow tint PT 144 3 Imron .RTM. Magenta tint PT 164 6 Imron
.RTM. Black tint PT 105 19 Imron .RTM. Transparent yellow oxide
tint 101 PT 183 Imron .RTM. Medium fine aluminum tint PT 159 110
Ethyl acetate from Eastman Chemical, 65 Kingsport, Tennessee Imron
.RTM. Activator 15305S (in 250 crosslinking component Total 1049
Test Results Basecoat Sag dry film thickness 4 mils (101.6 microns)
R (orange peel) at BC dry film 5 thickness of 1.5 mils (38.1
microns) measured by ASTM D3451 DOI at Base Coat dry film thickness
of 75 1.5 mils (38.1 microns) measured by ASTM D5767 Test
Observations good sag resistance and very smooth and good DOI
Unless stated otherwise, all the ingredients were supplied by
Axalta Coating Systems, LLC of Wilmington, Delaware. Note: (1)-(3)
same as in Table 1.
TABLE-US-00003 TABLE 3 Coating System of Comparative Example 3
[Base coat having a dry cured coating thickness of 1.5 mils (38.1
microns) coated with Imron .RTM. Elite clear coat having a dry
cured coating thickness of 2 mils (50.8 microns) both bake cured
simultaneously for 30 minutes at high bake temperature of
180.degree. F. (82.2.degree. C.)] Base Coat Ingredients In grams
Polyurea binder prepared by Procedure 2 400 Low bake temperature
control agent 0 prepared by Procedure 3 Silica dispersion (1) 0
Acid functional acrylic copolymer (2) 0 Polyester (3) 50 Imron
.RTM. Yellow tint PT 144 3 Imron .RTM. Magenta tint PT 164 6 Imron
.RTM. Black tint PT 105 19 Imron .RTM. Transparent yellow oxide
tint 101 PT 183 Imron .RTM. Medium fine aluminum tint PT 159 110
Ethyl acetate from Eastman Chemical, 65 Kingsport, Tennessee Imron
.RTM. Activator 15305S (in 250 crosslinking component Total 1054
Test Results Basecoat Sag dry film thickness 3 mils (76.2 microns)
R (orange peel) at BC dry film 6 thickness of 1.5 mils (38.1
microns) measured by ASTM D3451 DOI at Base Coat dry film thickness
of 78 1.5 mils (38.1 microns) measured by ASTM D5767 Test
Observations good sag resistance and very smooth and good DOI
Unless stated otherwise, all the ingredients were supplied by
Axalta Coating Systems, LLC of Wilmington, Delaware. Note: (1)-(3)
same as in Table 1.
TABLE-US-00004 TABLE 4 Coating System of Comparative Example 4
[Base coat having a dry cured coating thickness of 1.5 mils (38.1
microns) coated with Imron .RTM. Elite clear coat having a dry
cured coating thickness of 2 mils (50.8 microns) both bake cured
simultaneously for 20 minutes at low bake temperature of
160.degree. F. (71.1.degree. C.)] Base Coat Ingredients In grams
Polyurea binder prepared by Procedure 2 0 Low bake temperature
control agent 0 prepared by Procedure 3 Silica dispersion (1) 0
Acid functional acrylic copolymer (2) 250 Polyester (3) 197 Imron
.RTM. Yellow tint PT 144 3 Imron .RTM. Magenta tint PT 164 6 Imron
.RTM. Black tint PT 105 19 Imron .RTM. Transparent yellow oxide
tint 101 PT 183 Imron .RTM. Medium fine aluminum tint PT 159 110
Ethyl acetate from Eastman Chemical, 65 Kingsport, Tennessee Imron
.RTM. Activator 15305S (in 250 crosslinking component Total 1051
Test Results Basecoat Sag dry film thickness 1 mil (25.4 microns) R
(orange peel) at BC dry film 4 thickness of 1.5 mils (38.1 microns)
measured by ASTM D3451 DOI at Base Coat dry film thickness of 50
1.5 mils (38.1 microns) measured by ASTM D5767 Test Observations
weak sag resistance and reduction in DOI Unless stated otherwise,
all the ingredients were supplied by Axalta Coating Systems, LLC of
Wilmington, Delaware.
TABLE-US-00005 TABLE 5 Coating System of Comparative Example 5
[Base coat having a dry cured coating thickness of 1.5 mils (38.1
microns) coated with Imron .RTM. Elite clear coat having a dry
cured coating thickness of 2 mils (50.8 microns) both bake cured
simultaneously for 20 minutes at low bake temperature of
160.degree. F. (71.1.degree. C.)] Base Coat Ingredients In grams
Polyurea binder prepared by Procedure 2 0 Low bake temperature
control agent 0 prepared by Procedure 3 Silica dispersion.sup.(1)
224 Acid functional acrylic copolymer.sup.(2) 76 Polyester.sup.(3)
146 Imron .RTM. Yellow tint PT 144 3 Imron .RTM. Magenta tint PT
164 6 Imron .RTM. Black tint PT 105 19 Imron .RTM. Transparent
yellow oxide tint 101 PT 183 Imron .RTM. Medium fine aluminum tint
PT 159 110 Ethyl acetate from Eastman Chemical, 65 Kingsport,
Tennessee Imron .RTM. Activator 15305S (in 250 crosslinking
component Total 1049 Test Results Basecoat Sag dry film thickness 4
mils (101.6 microns) R (orange peel) at BC dry film 3 thickness of
1.5 mils (38.1 microns) measured by ASTM D3451 DOI at Base Coat dry
film thickness of 61 1.5 mils (38.1 microns) measured by ASTM D5767
Test Observations good sag resistance, but peely Unless stated
otherwise, all the ingredients were supplied by Axalta Coating
Systems, LLC of Wilmington, Delaware. Note: .sup.(1)-(3)same as in
Table 1.
TABLE-US-00006 TABLE 6 Coating System of Comparative Example 6
[Base coat having a dry cured coating thickness of 1.5 mils (38.1
microns) coated with Imron .RTM. Elite clear coat having a dry
cured coating thickness of 2 mils (50.8 microns) both bake cured
simultaneously for 20 minutes at low bake temperature of
160.degree. F. (71.1.degree. C.)] Base Coat Ingredients In grams
Polyurea binder prepared by Procedure 2 400 Low bake temperature
control agent 0 prepared by Procedure 3 Silica dispersion.sup.(1) 0
Acid functional acrylic copolymer.sup.(2) 0 Polyester.sup.(3) 50
Imron .RTM. Yellow tint PT 144 3 Imron .RTM. Magenta tint PT 164 6
Imron .RTM. Black tint PT 105 19 Imron .RTM. Transparent yellow
oxide tint 101 PT 183 Imron .RTM. Medium fine aluminum tint PT 159
110 Ethyl acetate from Eastman Chemical, 65 Kingsport, Tennessee
Imron .RTM. Activator 15305S (in 250 crosslinking component Total
1054 Test Results Basecoat Sag dry film thickness 2 mils (50.8
microns) R (orange peel) at BC dry film 5 thickness of 1.5 mils
(38.1 microns) measured by ASTM D3451 DOI at Base Coat dry film
thickness of 65 1.5 mils (38.1 microns) measured by ASTM D5767 Test
Observations medium sag resistance and smooth Unless stated
otherwise, all the ingredients were supplied by Axalta Coating
Systems, LLC of Wilmington, Delaware.
TABLE-US-00007 TABLE 7 Coating System of Example 1 of the Present
Invention [Base coat having a dry cured coating thickness of 1.5
mils (38.1 microns) coated with Imron .RTM. Elite clear coat having
a dry cured coating thickness of 2 mils (50.8 microns) both bake
cured simultaneously for 20 minutes at low bake temperature of
160.degree. F. (71.1.degree. C.)] Base Coat Ingredients In grams
Polyurea binder prepared by Procedure 2 0 Low bake temperature
control agent 300 prepared by Procedure 3 Silica dispersion.sup.(1)
0 Acid functional acrylic copolymer.sup.(2) 0 Polyester.sup.(3) 146
Imron .RTM. Yellow tint PT 144 3 Imron .RTM. Magenta tint PT 164 6
Imron .RTM. Black tint PT 105 19 Imron .RTM. Transparent yellow
oxide tint 101 PT 183 Imron .RTM. Medium fine aluminum tint PT 159
110 Ethyl acetate from Eastman Chemical, 65 Kingsport, Tennessee
Imron .RTM. Activator 15305S (in 250 crosslinking component Total
1049 Test Results Basecoat Sag dry film thickness 5 mils (127
microns) R (orange peel) at BC dry film 7 thickness of 1.5 mils
(38.1 microns) measured by ASTM D3451 DOI at Base Coat dry film
thickness of 80 1.5 mils (38.1 microns) measured by ASTM D5767 Test
Observations good sag resistance and very smooth and good DOI
Unless stated otherwise, all the ingredients were supplied by
Axalta Coating Systems, LLC of Wilmington, Delaware. Note:
.sup.(1)-(3)same as in Table 1
TABLE-US-00008 TABLE 8 Ambient Temperature Curing [Comparative
Examples 7 and 8 coatings were cured for 24 hours at ambient
temperature in a range of from 60.degree. F. (15.degree. C.) to
110.degree. F. (43.degree. C.) (Ingredient in grams)] Comparative 7
Comparative 8 Silica dispersion.sup.(1) 10 0 BENTONE .RTM.
dispersion.sup.(4) 0 0 GARAMITE .RTM. dispersion.sup.(5) 0 0 Low
bake temperature 0 37.0 control agent prepared by Procedure 3 Acid
functional acrylic 8.8 4.0 copolymer.sup.(2) Polyester.sup.(3) 18
15.0 Violet tint PT 120 0.1 0.1 Blacktint PT 105 0.5 0.5 Blue tint
PT 122 3.9 3.9 Red shade blue tint PT 124 11.2 11.2 Aluminum tint
PT 114 10.9 10.9 Methyl amyl ketone 14.0 10.0 Ethyl acetate 10.9
5.0 Butyl acetate 6.5 3.0 Heptane 1.7 1.7 Ethyl 3-ethoxy propionate
2.1 2.3 Dibutyl tin dilurate 0.01 0.01 Imron .RTM. Activator 15305S
35.0 36 Total [grams] 133.6 140.6 Test Results Minimum Dry Film 4 3
Thickness for Sag [mil] R (orange peel) of dry film 5 8 thickness
of 1.5 mils measured by ASTM D3451 DOI of dry film thickness of 70
75 1.5 mils measured by ASTM D5767 Mottle measurement.sup.(6) 6.7
4.5 Coating appearance Good sag resistance Medium sag but peely and
poor resistance, smooth mottle resistance and good mottle
resistance Unless stated otherwise, all the ingredients were
supplied by Axalta Coating Systems, LLC of Wilmington, Delaware.
Note: .sup.(1)-(3)same as in Table 1. .sup.(4)The BENTONE .RTM.
clay was from Elementis Specialties, London, United Kingdom, under
respective registered trademark. BENTONE .RTM. 34 dispersion was
prepared according to U.S. Pat. No. 8,357,456, herein incorporated
by reference. .sup.(5)GARAMITE .RTM. clay was from Southern Clay
Products, Gonzales, TX, USA, under respective registered trademark.
GARAMITE .RTM. dispersion was prepared according to U.S. Pat. No.
8,227,544, herein incorporated by reference. .sup.(6)Mottle
measurement was performed using Cloud Runner available from
BYK-Gardner GmbH, Geretsried, Germany.
TABLE-US-00009 TABLE 9 Ambient Temperature Curing [Examples 2-4
coatings were cured for 24 hours at ambient temperature in a range
of from 60.degree. F. (15.degree. C.) to 110.degree. F. (43.degree.
C.) (Ingredient in grams) Example 2 Example 3 Example 4 Silica
dispersion.sup.(1) 4.0 0.0 0.0 BENTONE .RTM. dispersion.sup.(4) 0.0
10.0 0.0 GARAMITE .RTM. dispersion.sup.(5) 0.0 0.0 10.0 Low bake
temperature 18.0 18.0 18.0 control agent prepared by Procedure 3
Acid functional acrylic 3.9 2.0 2.0 copolymer.sup.(2)
Polyester.sup.(3) 16.7 13.0 13.0 Violet tint PT 120 0.1 0.1 0.1
Blacktint PT 105 0.5 0.5 0.5 Blue tint PT 122 3.9 3.9 3.9 Red shade
blue tint PT 124 11.2 11.2 11.2 Aluminum tint PT 114 10.9 10.9 10.9
Methyl amyl ketone 10.0 14.0 14.0 Ethyl acetate 15.0 10.9 10.9
Butyl acetate 4.1 6.5 6.5 Heptane 1.8 1.7 1.7 Ethyl 3-ethoxy
propionate 1.2 2.1 2.1 Dibutyl tin dilurate 0.01 0.01 0.01 Imron
.RTM. Activator 15305S 35.5 35.0 35.0 Total [grams] 136.8 139.8
139.8 Test Results Minimum Dry Film 4 4 4 Thickness for Sag [mil] R
(orange peel) of dry film 7 7 7 thickness of 1.5 mils measured by
ASTM D3451 DOI of dry film thickness of 73 75 76 1.5 mils measured
by ASTM D5767 Mottle measurement.sup.(6) 5.1 5.0 5 Coating
appearance Good sag Good sag Good sag resistance, resistance,
resistance, very smooth, very smooth, very smooth, good DOI good
DOI good DOI and and and good mottle good mottle good mottle
resistance resistance resistance Unless stated otherwise, all the
ingredients were supplied by Axalta Coating Systems, LLC of
Wilmington, Delaware. Note: .sup.(1)-(6)same as in Table 7.
[0086] From the foregoing, it would be clear to one of ordinary
skill in the art that:
[0087] 1. It is the unique combination of components within the low
bake cure temperature control agent that gives rise to increasing
sag resistance of the resultant coating;
[0088] 2. The low bake cure temperature cure agent also
simultaneously provides desired coating properties, such as smooth
surface, and very good DOI (distinctness of image).
[0089] 3. The low bake cure temperature cure agent produces a
coating composition having low VOC at low bake temperatures in
shorter cure times than the prior art.
[0090] Accordingly, various embodiments for low VOC (volatile
organic component) low bake temperature curable coating
compositions suitable for use in automotive OEM (original equipment
manufacturer) and refinish applications and processes for producing
coatings at low bake temperatures are described herein. While at
least one exemplary embodiment has been presented in the foregoing
detailed description of the invention, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiment or exemplary embodiments
are only examples, and are not intended to limit the scope,
applicability, or configuration of the invention in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention. It being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended
claims.
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